JP2000247633A - Planar mg-al base hydrotalcite type grain powder and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain Mg-Al base grain powder having a specific tabular ratio and composition under atmospheric pressure by mixing a magnesium compound and aluminum compound at least one of which exhibits a tabular shape and firing the mixture to obtain a tabular Mg-Al-multi component oxide, then hydrating the mixture by an aqueous solution containing anion. SOLUTION: The magnesium compound and the aluminum compound at least one of which exhibits the tabular shape are mixed. This mixture is fired at 400 to 550 deg.C, by which the tabular Mg-Al-multi component oxide is obtained. This multi component oxide is then hydrated for 2 to 24 hours at 20 to 100 deg.C by the aqueous solution containing the anion. The multi component oxide is subjected to water washing and drying after the end of the hydration, by which the tabular Mg-Al base hydrotalcite type grain powder is obtained. The formed tabular grains are 10 to 100 in the planar ratio (plate surface diameter/ thickness), 0.05 to 0.5 μm in tabular surface diameter, 30 to 130 m3/g in BET specific surface area and 0.2<=x<0.9 in the content ratio x when Mg:Al=1-x:x is defined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet ratio (sheet surface diameter /
(Thickness) is related to Mg-Al-based hydrotalcite-type particles.

[0002]

2. Description of the Related Art As well known, there are various kinds of layered compounds other than clay minerals and the like. Among them, layered double hydroxides such as hydrotalcite are known.
(Ultra Hydroxide) has a structure in which various ions and molecules can be inserted between layers, so that an anion exchange function can be exhibited.

[0003] Generally, the structure of hydrotalcite is
Described in the journal of the Chemical Society of Japan, 1995 (8), pp. 622-628.
As mentioned, "[M²⁺ _1-xM³⁺ _x(OH)₂]_x ⁺[An⁻
_{x / n}・ YH₂O]_x ⁻  Where M²⁺Is Mg²⁺, Co²⁺, Ni²⁺, Zn
²⁺Divalent metal ions such as M³⁺Is Al³⁺, Fe
³⁺, Cr³⁺Trivalent metal ions such as An⁻Is OH
⁻, Cl⁻, CO₃ ^2-, SO₄ ^2-N-valent shades such as
On, x typically ranges from 0.2 to 0.33. Conclusion
The crystal structure is a octahedral brucite unit with a positive charge.
It consists of a two-dimensional base layer in which
It has a laminated structure. "It is.

[0004] Hydrotalcite has been used as an antacid for a long time. After that, however, it has been developed for various applications utilizing an anion exchange function. For example, an ion exchange material, an adsorbent, a deodorant, It is used for a wide variety of applications such as stabilizers for resins and rubbers such as polyethylene, polypropylene and vinyl chloride, as well as paints, various catalysts, agricultural films and inks.

[0005] In addition, at present, when consideration is given to the environment, it is desired to use an additive which does not contain a toxic metal. It can be said that the hydrotalcite-type particle powder, which is a compound, can meet such expectations.

[0006] In particular, since among the hydrotalcite-type particles, Mg 2 ⁺ as the divalent metal ^ion, Mg-Al-based hydrotalcite-type particles having Al ³⁺ as the trivalent metal ion is stable, It is the one that has received the most attention.

The hydrotalcite-type particles generally have a plate-like shape, and the particles tend to be oriented due to the shape. Therefore, when it is formed into a coating film, it has excellent properties of covering property and shielding property, so that it is promising for applications such as undercoat paints for automobiles, rust preventive materials, and paints having gas barrier properties. In order to obtain a coating film excellent in covering property and shielding property, hydrotalcite-type particle powder having a large plate ratio and excellent orientation is required.

[0008] Examples of the hydrotalcite-type particle powder include iron-based hydrotalcite-type particle powder (Japanese Patent Application Laid-Open No. 9-227127). When it is used as a paint, it becomes a colored paint, which causes inconvenience as an undercoat paint.

As a method for producing hydrotalcite-type particles, an aqueous solution of a metal salt containing a divalent metal ion and a trivalent metal ion constituting a basic layer and an aqueous solution containing an anion constituting an intermediate layer are mixed. In general, a method of controlling the temperature, pH and the like to obtain a coprecipitation reaction is used. In addition to the reaction under normal pressure, a method is also known in which the reaction is obtained by a hydrothermal reaction using an autoclave. Further, a method of firing a hydrotalcite-type particle powder obtained by a coprecipitation reaction to obtain a composite oxide, and then hydrating the composite oxide with an aqueous solution containing an anion to obtain a hydrotalcite-type particle powder (Reconstruction method) is also known.

[0010]

SUMMARY OF THE INVENTION A plate M having a large plate ratio
The g-Al-based hydrotalcite-type particle powder, which is currently most demanded, is Mg-A that sufficiently satisfies the property that the particles are easily oriented due to the plate-like shape.
1-based hydrotalcite-type particle powder has not been provided yet.

That is, in the above-mentioned coprecipitation reaction, it is difficult to obtain hydrotalcite-type particles having a large plate-like ratio.
Due to the reaction of the aqueous solution, the product is a soluble salt (eg,
Alkali metal salts such as sodium and sulfates).

In addition, the hydrothermal reaction requires an autoclave.

Further, since the hydrotalcite-type particles obtained by the restructuring method use the hydrotalcite-type particles obtained by the coprecipitation reaction as a starting material, the particle shape and plate ratio of the starting material are reduced. Since it is inherited, it is difficult to obtain hydrotalcite-type particles having a large plate ratio.

Therefore, the present invention provides a plate-shaped M having a large plate-shaped ratio.
It is a technical object to obtain g-Al-based hydrotalcite-type particles under normal pressure.

[0015]

The above technical object can be achieved by the present invention as described below.

That is, in the present invention, the plate ratio (plate surface diameter / thickness)
Is 10 to 100, and the plate surface diameter is 0.05 to 0.5 μm.
m, and the composition ratio x when Mg: Al = 1-x: x is 0.2 ≦ x ≦ 0.9, wherein the plate-like Mg—Al-based hydrotalcite-type particles are characterized by the following formula: It is.

Further, according to the present invention, a plate-like Mg-Al composite oxide is obtained by mixing a magnesium compound and an aluminum compound, at least one of which has a plate-like shape, and firing the mixture at 400 to 550 ° C. And then hydrating the composite oxide with an aqueous solution containing anions. The method for producing plate-like Mg-Al-based hydrotalcite-type particles described above, wherein the composite oxide is hydrated.

The configuration of the present invention will be described in more detail as follows.

First, the Mg-Al-based hydrotalcite-type particles according to the present invention will be described.

The particle shape of the Mg-Al-based hydrotalcite-type particles according to the present invention is plate-like.

The Mg-Al-based hydrotalcite-type particles according to the present invention have a plate-like ratio of 10 to 100. When the tabular ratio is less than 10, the orientation is insufficient, which is not preferable. If it exceeds 100, it will be difficult to produce it industrially. Preferably, it is 12-100.

The Mg-Al-based hydrotalcite-type particles according to the present invention have a plate surface diameter of 0.05 to 0.5 µm. When the plate surface diameter is less than 0.05 μm, the dispersibility in the paint is insufficient. If it exceeds 0.5 μm, it is difficult to produce industrially. Preferably 0.07
０．５0.5 μm.

The thickness of the Mg—Al-based hydrotalcite-type particles according to the present invention is 0.005 to 0.050 μm.
Is preferable, and more preferably 0.005 to 0.040 μm
m.

The BET specific surface area value of the Mg-Al-based hydrotalcite-type particles according to the present invention is 30 to 130 m
² / g, more preferably 35~130m ² /
g.

The composition of the Mg-Al-based hydrotalcite-type particles according to the present invention is as follows.

[0026] _{Mg 1-x · Al x ·} (OH) 2 · A n-
_{x / n} · mH ₂ O A: n-valent anion, 0.2 ≦ x ≦ 0.9, m> 0

The composition ratio x of the Mg-Al-based hydrotalcite-type particles according to the present invention when Mg: Al = 1-x: x is 0.2 to 0.9. When x is less than 0.2 or more than 0.9, it is difficult to obtain a single phase of Mg-Al-based hydrotalcite-type particles. A preferable range of x is 0.22 to 0.9.

The anion (A) is not particularly specified, and includes OH ⁻ , CO ₃ ^{2- and the} like, and is preferably CO ₃ ^2- .

The Mg-Al-based hydrotalcite-type particles according to the present invention have a low content of sulfur compounds or sulfate ions due to the production method described later. The content of the sulfur compound or the sulfate ion is 50 ppm or less in S conversion.

The degree of orientation of the Mg-Al hydrotalcite-type particles according to the present invention is preferably at least 65%, more preferably at least 70%. The degree of orientation of the hydrotalcite-type particles was measured by the method described below.

Next, a method for producing the Mg-Al-based hydrotalcite-type particles according to the present invention will be described.

The Mg-Al-based hydrotalcite-type particles according to the present invention are obtained by mixing a magnesium compound and an aluminum compound, at least one of which has a plate shape, and baking the mixture at 400 to 550 ° C. It can be obtained by obtaining an Al composite oxide and hydrating the composite oxide with an aqueous solution containing an anion.

As the magnesium compound in the present invention, magnesium hydroxide, magnesium oxide, magnesium chloride, basic magnesium carbonate, magnesium acetate, magnesium nitrate and the like can be used. Preferably, it is magnesium hydroxide.

The aluminum compound in the present invention includes aluminum hydroxide, aluminum oxide, aluminum chloride, sodium aluminate, aluminum acetate,
Aluminum nitrate or the like can be used. Preferably, it is aluminum hydroxide.

At least one of the magnesium compound and the aluminum compound has a plate shape. Preferably, both have a plate shape.

The mixing of the magnesium compound and the aluminum compound may be performed using a mortar, a ball mill, or the like.

The firing temperature of the Mg—Al mixture is 400 to
550 ° C. If the temperature is lower than 400 ° C or higher than 550 ° C, compounds other than hydrotalcite-type particles are generated, which is not preferable. Preferably 450-540 ° C
It is.

The aqueous solution for hydrating the Mg-Al composite oxide may be any aqueous solution containing anions to be present in the hydrotalcite-type particle powder, and is preferably an aqueous carbonate solution. Specifically, it is a sodium carbonate aqueous solution.

The concentration of the aqueous solution containing the anion is as follows:
0.1-3.0 mol / l is preferable.

The temperature of the aqueous solution for hydrating the Mg—Al composite oxide is preferably from 20 to 100 ° C.

The time for hydrating the Mg—Al composite oxide is as follows:
Preferred is 2 to 24 hours.

After completion of the hydration, the resultant is washed with water and dried to obtain plate-like Mg-Al-based hydrotalcite-type particles.

[0043]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical embodiment of the present invention is as follows.

The particle shapes of the magnesium compound and the aluminum compound were determined from electron micrographs.

The plate surface diameter of the hydrotalcite-type particles is indicated by the average value of the values measured from an electron micrograph.

The thickness of the particles of the hydrotalcite-type particles was measured using an X-ray diffractometer RAD-2A (Rigaku Corporation).
(Tube: Fe, tube voltage: 40 kV, tube current: 20)
mA, goniometer: wide-angle goniometer, sampling width: 0.010 °, scanning speed: 0.500 ° / mi
n, divergence slit: 1 °, scattering slit: 1 °, light receiving slit: 0.30 mm), and calculated from the diffraction peak curve of the (003) crystal plane of the hydrotalcite-type particles using Scherrer's equation. It is indicated by a value.

The obtained particle powder was identified by X-ray diffraction, and the diffraction angle 2θ was 5 to 5 using the X-ray diffractometer.
Measured at 90 °.

The BET specific surface area value is shown by a value measured by the BET method.

Structural formula in Mg-Al-based hydrotalcite type particle powder: Mg _1-x .Al _x. (OH) ₂ .A ⁿ _{-x /} n.mH
The index x in ₂ O is obtained by dissolving the Mg—Al-based hydrotalcite-type particles with an acid and using a plasma emission spectrometer.
SPS4000 (Seiko Electronics Industry Co., Ltd.) ".

The carbon content (% by weight) and the content of sulfur compound or sulfate ion when CO ₃ ^{2- is} used as the anion (A ⁿ⁻ ) are measured by a carbon sulfur analyzer: EMIA-2200 (manufactured by HORIBA). did.

The degree of orientation (%) of the Mg—Al-based hydrotalcite-type particles was evaluated by the following method.

1.5 g of hydrotalcite type particle powder,
1 cc of castor oil and 3.5 g of lacquer are thoroughly mixed to form a paint, and applied to the coated paper with an applicator (GAP 150 μm). By taking the scattering vector perpendicular to the obtained coating film and using the X-ray diffractometer, the diffraction angle 2θ was 5 °.
Measure in the range of ９０90 °.

From the X-ray diffraction measurement results obtained,
The degree of orientation is calculated by the following equation described in JP-A-6-35004.

(Equation 1)

Here, I indicates the integrated intensity of the diffraction peak.
And the suffixes A and R indicate an oriented sample and a non-oriented sample, respectively.
You. ΣI_A00l and ΔI_R001 is the surface index (00
3) Diffraction peak intensities on each surface of (006) and (009)
Indicates the sum of degrees,_Atotal and I _Rtotal is times
Shows the sum of all peak intensities when angle 2θ is 5 to 90 °
Things.

The plate surface of the Mg—Al-based hydrotalcite-type particles according to the present invention is parallel to the (001) plane of the hydrotalcite-type structure. Therefore, the orientation degree is (00
1) It is for evaluating the relative ratio of the reflection intensity of the surface parallel to the surface, and is a relative evaluation of how the plate surface of the plate-like particles in the coating film faces the film surface.

<Production Method of Mg-Al Hydrotalcite Type Particle Powder> Magnesium hydroxide powder 58.32 g and aluminum hydroxide powder 78.00 g are sufficiently mixed using a mortar. The resulting mixture is heated at 500 ° C. in air for 2 hours.
After firing for a time, a plate-like Mg-Al-based composite oxide powder was obtained.

The obtained powder (22.82 g) was treated with 0.35 mol
The solution was added to 500 ml of a 1 / l aqueous sodium carbonate solution to make the total amount 1 l, and aged at 95 ° C. for 5 hours with stirring to obtain a white precipitate.

The resulting white precipitate was filtered, washed with water, and washed with water.
Drying at 0 ° C. gave a white particle powder. As a result of identifying this white particle powder by X-ray diffraction, it was confirmed that it was hydrotalcite-type particle powder.

The obtained plate-like Mg-Al-based hydrotalcite-type particles have an average plate diameter of 0.30 μm, a thickness of 0.0138 μm, a plate ratio of 21.7 and a BET specific surface area of 70. 5 m ² / g, and the degree of orientation was 85%.

[0060]

The important point in the present invention is that the plate ratio is 10 to 1
It is said that the hydrotalcite-type particle powder having a specific composition having a plate surface diameter of 0.05 to 0.5 μm has a large plate-like ratio and, when formed into a coating film, has excellent orientation. That is.

The excellent orientation when the Mg-Al-based hydrotalcite-type particles according to the present invention is formed into a coating film is due to the large plate-like ratio of the Mg-Al-based hydrotalcite-type particles. It is considered that the hydrotalcite-type particle powder is easily oriented when a coating film is formed.

The reason why the plate-like ratio of the Mg-Al-based hydrotalcite-type particles according to the present invention is large is that the Mg-Al composite oxide obtained by mixing and firing an aluminum compound and a magnesium compound has a plate shape. Shape, and the plate-like ratio is large, so that the Mg-Al-based hydrotalcite-type particles obtained by hydrating the same retain their shape,
This is because a particle powder having a large tabular ratio can be obtained.

Further, a mixture of a magnesium compound and an aluminum compound is calcined to obtain plate-like Mg-Al-based composite oxide particles, and the particles are hydrated to directly obtain hydrotalcite-type particles. Thus, hydrotalcite-type particles having a desired composition can be easily obtained. Further, since the amount of sulfur compounds or sulfate ions is small, a coating film having excellent corrosion resistance can be formed, which is suitable as a rust preventive paint.

[0064]

Next, examples and comparative examples will be described.

Examples 1 to 9 and Comparative Examples 1 to 3 The same procedure as in the above embodiment of the present invention was carried out except that the type of magnesium compound, the type of aluminum compound, the mixing amount and the firing temperature were variously changed. Hydrotalcite-type particle powder was obtained.

The main manufacturing conditions at this time are shown in Table 1, and the obtained M
Table 2 shows properties of the g-Al-based hydrotalcite-type particles.

[0067]

[Table 1]

[0068]

[Table 2]

Comparative Example 4 (Production of Hydrotalcite-Type Particle Powder by Coprecipitation Reaction) 500 ml of an aqueous sodium carbonate solution having a CO ₃ ^2- ion concentration of 0.875 mol / l and 3 l of an aqueous sodium hydroxide solution having a 5.208 mol / l concentration were mixed. Mix, keep at 60 ° C. and stir in reaction vessel. 3.75 mol to this
/ L of magnesium sulfate aqueous solution 500ml and 0.625
After adding 500 ml of a mol / l aluminum sulfate aqueous solution, the total amount was adjusted to 5 l. It aged at 95 degreeC for 15 hours, stirring the inside of a reaction container. The pH value of the suspension during aging was 12.2. After filtration and washing with water, the particles were dried at 60 ° C. to obtain white particle powder. As a result of identifying this white particle powder by X-ray diffraction, it was confirmed that it was hydrotalcite-type particle powder.

The obtained Mg-Al-based hydrotalcite-type particles had an average plate surface diameter of 0.07 μm and a thickness of 0.1 μm.
0125 μm, the plate ratio was 5.6, the BET specific surface area was 85.5 m ² / g, and the degree of orientation was 48%.

Table 2 shows properties of the obtained Mg-Al hydrotalcite-type particles.

Comparative Example 5 (Production of Hydrotalcite-Type Particle Powder by Reconstruction Method) Hydrotalcite-type Particle Powder 20 Obtained in Comparative Example 4
g in air at 500 ° C. for 2 hours.
Based composite oxide particles were obtained. 10. Obtained particle powder
74 g was added to 250 ml of a 0.175 mol / l sodium carbonate aqueous solution to make the total amount 500 ml, and the mixture was aged at 95 ° C. for 5 hours with stirring to obtain a white precipitate. As a result of identifying this white particle powder by X-ray diffraction, it was confirmed that it was hydrotalcite-type particle powder.

The obtained Mg-Al-based hydrotalcite-type particles have an average plate surface diameter of 0.07 μm and a thickness of 0.1 μm.
It was 0115 μm, the plate ratio was 6.1, the BET specific surface area was 88.8 m ² / g, and the degree of orientation was 50%.

Table 2 shows the properties of the obtained Mg-Al hydrotalcite-type particles.

[0075]

The plate-like Mg-Al-based hydrotalcite-type particles according to the present invention have a large plate-like ratio and a high orientation, and thus are suitable as undercoat paints for automobiles and rust preventive paints.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akinori Yamamoto 4-1-2, Funariminami, Naka-ku, Hiroshima-shi, Hiroshima Toda Kogyo Co., Ltd. Creative Center F-term (reference) 4G076 AA18 AA19 AB02 AB04 AB06 AB09 AB12 BA24 BA39 BC07 BC08 BD02 CA02 CA08 CA22 CA28 CA36 DA01 DA16 DA25 DA30

Claims (2)

[Claims] 1. A plate ratio (plate surface diameter / thickness) of 10 to 100.
And the plate surface diameter is 0.05 to 0.5 μm;
The composition ratio x when g: Al = 1−x: x is 0.2
≤ x ≤ 0.9, wherein the plate-like Mg-Al-based hydrotalcite-type particles powder. 2. A mixture of a magnesium compound and an aluminum compound, at least one of which has a plate-like shape, and firing the mixture at 400 to 550 ° C.
The method for producing plate-like Mg-Al-based hydrotalcite-type particles according to claim 1, wherein the composite oxide is obtained, and then the composite oxide is hydrated with an aqueous solution containing an anion.